Lighter-than-air airships maintain their buoyancy using lifting gas contained in a rigid or non-rigid hull. The lifting gas is typically a light gas such as hydrogen or helium. These lifting gasses can diffuse through an undamaged hull and rapidly leak through macroscopic holes and tears in damaged hull sections. A macroscopic hole or tear (hereinafter generally discussed as a “hole”) can lead to rapid loss of lifting gas, loss of altitude, and potentially loss of the entire airship. The problem is particularly severe for very high altitude airships intended for stratospheric operation, where the hull material may be relatively light-weight and therefore prone to damage. For example, JAXA reported in 2008 regarding a flight experiment performed the previous year. A 300,000 m3 balloon, with a hull comprised of Heptax, was successfully launched from Brazil on Nov. 20, 2007. However, it burst at an altitude of 14.7 km. JAXA theorized that the balloon may have suffered damage around the balloon spooler or collar. JAXA has also noted that unexpected gusty wind conditions during balloon inflation could lead to severe damage. Even if prompt loss of the airship is avoided, a small hole will result in a significant loss of lifting gas over time, thereby leading to a loss of altitude and a relatively rapid termination of the mission. A small hole can be caused, for example, by a natural micrometeorite or a man-made projectile such as a bullet or a piece of man-made space debris falling back into the atmosphere, as well as ongoing abrasion, excessive stress due to wind gusts, and other factors.
If a way could be found to minimize the likelihood of catastrophic damage, and rapidly repair lightly-damaged hulls “in situ” (i.e., while the airship is still at altitude), the rapid loss of lifting gas could be prevented or halted and adverse consequences could be minimized.
This invention is directed to the problem of airship hull robustness and in situ airship hull repair.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.